U.S. patent application number 14/200929 was filed with the patent office on 2014-09-18 for illumination device and projector.
This patent application is currently assigned to SEIKO EPSON CORPORATION. The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Koichi AKIYAMA, Akihiro KASHIWAGI.
Application Number | 20140268067 14/200929 |
Document ID | / |
Family ID | 51525866 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140268067 |
Kind Code |
A1 |
AKIYAMA; Koichi ; et
al. |
September 18, 2014 |
ILLUMINATION DEVICE AND PROJECTOR
Abstract
A illumination device includes a light source, a diffractive
optical element on which light emitted from the light source is
made incident, and a superimposing optical system on which
diffracted light emitted from the diffractive optical element is
made incident. A direction of a principal ray in the center of the
diffracted light coincides with an optical axis of the
superimposing optical system. Consequently, it is possible to
reduce an aberration due to the superimposing optical system and to
emit illumination light having a more uniform illuminance
distribution.
Inventors: |
AKIYAMA; Koichi;
(Matsumoto-Shi, JP) ; KASHIWAGI; Akihiro;
(Shiojiri-Shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
51525866 |
Appl. No.: |
14/200929 |
Filed: |
March 7, 2014 |
Current U.S.
Class: |
353/31 ; 353/30;
359/15; 359/567 |
Current CPC
Class: |
H04N 9/3152 20130101;
G02B 5/1842 20130101; G02B 5/32 20130101; H04N 9/3161 20130101;
G02B 27/1066 20130101; G02B 27/141 20130101 |
Class at
Publication: |
353/31 ; 359/567;
359/15; 353/30 |
International
Class: |
H04N 9/31 20060101
H04N009/31; G02B 5/32 20060101 G02B005/32; G02B 27/10 20060101
G02B027/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2013 |
JP |
2013-053728 |
Claims
1. A illumination device comprising: a light source; a diffractive
optical element on which light emitted from the light source is
made incident; and a superimposing optical system on which
diffracted light emitted from the diffractive optical element is
made incident, wherein a direction of a principal ray in the center
of the diffracted light coincides with an optical axis of the
superimposing optical system.
2. The illumination device according to claim 1, wherein the light
emitted from the light source is perpendicularly made incident on a
light incident surface of the diffractive optical element, and the
direction of the principal ray in the center of the diffracted
light is tilted with respect to an optical axis of the light
emitted from the light source.
3. The illumination device according to claim 2, wherein the
direction of the principal ray in the center of the diffracted
light is tilted at an angle of 5 to 20.degree. with respect to the
optical axis of the light emitted from the light source.
4. The illumination device according to claim 1, wherein the
superimposing optical system is configured by a lens group of at
least two lenses, the diffractive optical element is arranged at a
combined front focal position of the lens group, and an
illumination target is arranged at a combined rear focal position
of the lens group.
5. The illumination device according to claim 4, wherein the
diffracted light has a luminous intensity distribution of a
rectangular shape as a whole, an aspect ratio of the luminous
intensity distribution being equal to an aspect ratio of the
illumination target.
6. The illumination device according to claim 1, wherein the light
source and the diffractive optical element are arranged such that,
when the principal ray in the center of the diffracted light is set
to coincide with the horizontal direction, the light emitted from
the light source is made incident on the diffractive optical
element from upward to downward.
7. The illumination device according to claim 1, wherein a computer
generated hologram is used as the diffractive optical element.
8. The illumination device according to claim 1, wherein a
semiconductor laser is used as the light source.
9. The illumination device according to claim 1, wherein an array
light source in which a plurality of semiconductor lasers are
arrayed is used as the light source.
10. The illumination device according to claim 1, further
comprising a collimator optical system configured to convert the
light emitted from the light source into parallel light.
11. The illumination device according to claim 1, wherein an afocal
optical system is arranged between the light source and the
diffractive optical element.
12. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 1 is used as the illumination device.
13. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 2 is used as the illumination device.
14. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 3 is used as the illumination device.
15. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 4 is used as the illumination device.
16. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 5 is used as the illumination device.
17. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 6 is used as the illumination device.
18. A projector comprising: a illumination device configured to
emit illumination light; a light modulating device configured to
form image light obtained by modulating the illumination light
according to image information; and a projection optical system
configured to project the image light, wherein the illumination
device according to claim 7 is used as the illumination device.
19. The projector according to claim 12, wherein the light emitted
from the light source is linearly polarized light, and a liquid
crystal panel is used as the light modulating device.
20. The projector according to claim 12, wherein a plurality of the
illumination devices and a plurality of the light modulating
devices are arranged for respective illumination lights having
different wavelength regions, and a combining optical system
configured to combine image lights modulated for the respective
illumination lights having the different wavelength regions is
further provided.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates to a illumination device and a
projector.
[0003] 2. Related Art
[0004] There has been widely known a projector that illuminates a
light modulating device with illumination light emitted from a
illumination device, magnifies image light modulated and emitted by
the light modulating device, and projects the magnified image light
on a screen using a projection optical system.
[0005] As a light source of the illumination device included in the
projector, a laser light source such as a semiconductor laser (LD),
with which high-luminance and high-power light can be obtained,
attracts attention. Compared with a metal halide lamp, a halogen
lamp, and the like in the past, the laser light source has
advantages that the laser light source can be reduced in size, is
excellent in color reproducibility, can be lit instantaneously, and
has long life.
[0006] The related art is described in, for example, JP-A-11-64789
and JP-A-2000-162548.
[0007] In order to perform video display excellent in display
quality in the projector, it is necessary to improve uniformity of
an illuminance distribution of illumination light with which the
light modulating device serving as an illumination target is
irradiated.
SUMMARY
[0008] An advantage of some aspects of the invention is to provide
a illumination device that can emit illumination light having a
more uniform illuminance distribution and a projector including the
illumination device.
[0009] An aspect of the invention is directed to a illumination
device including: a light source; a diffractive optical element on
which light emitted from the light source is incident; and a
superimposing optical system on which diffracted light emitted from
the diffractive optical element is incident. A direction of a
principal ray in the center of the diffracted light coincides with
an optical axis of the superimposing optical system.
[0010] With the configuration of the illumination device, the
direction of the principal ray in the center of the diffracted
light coincides with the optical axis of the superimposing optical
system. Therefore, it is possible to emit illumination light having
a more uniform illuminance distribution while reducing an
aberration due to the superimposing optical system.
[0011] It is preferable that the light emitted from the light
source is perpendicularly incident on a light incident surface of
the diffractive optical element, and the direction of the principal
ray in the center of the diffracted light is tilted with respect to
an optical axis of the light emitted from the light source.
[0012] With this configuration, it is easy to perform diffractive
optical design of the diffractive optical element. Further, it is
possible to efficiently make the diffracted light emitted from the
diffractive optical element enter the superimposing optical
system.
[0013] It is preferable that the direction of the principal ray in
the center of the diffracted light is tilted at an angle of 5 to
20.degree. with respect to the optical axis of the light emitted
from the light source.
[0014] With this configuration, it is possible to emit illumination
light having a more uniform illuminance distribution while reducing
an aberration due to the superimposing optical system.
[0015] It is preferable that the superimposing optical system is
configured by a lens group of at least two lenses, the diffractive
optical element is arranged at a combined front focal position of
the lens group, and an illumination target is arranged at a
combined rear focal position of the lens group.
[0016] With this configuration, it is possible to efficiently make
light superimposed by the superimposing optical system incident on
the illumination target.
[0017] It is preferable that the diffracted light has a luminous
intensity distribution of a rectangular shape as a whole and that
an aspect ratio of the luminous intensity distribution is equal to
an aspect ratio of the illumination target.
[0018] With this configuration, it is possible to efficiently make
illumination light formed in a rectangular shape as a whole
incident on the illumination target formed in a rectangular
shape.
[0019] It is preferable that the light source and the diffractive
optical element are arranged such that, when the principal ray in
the center of the diffracted light is set to coincide with the
horizontal direction, the light emitted from the light source is
incident on the diffractive optical element from upward to
downward.
[0020] With this configuration, it is possible to suitably use the
illumination device as a illumination device for a projector.
[0021] A computer generated hologram can be used as the diffractive
optical element.
[0022] With this configuration, it is possible to generate
diffracted light with which diffraction efficiency of first order
diffracted light is maximized and to generate diffracted light
having a more uniform illuminance distribution.
[0023] A semiconductor laser can be used as the light source.
[0024] With this configuration, it is possible to obtain
high-luminance and high-power light and reduce the size of the
light source.
[0025] An array light source in which a plurality of the
semiconductor lasers are arrayed can be used as the light
source.
[0026] With this configuration, it is possible to obtain
higher-luminance and higher-power light using the array light
source in which the plurality of semiconductor lasers are
arrayed.
[0027] It is preferable that a collimator optical system configured
to convert the light emitted from the light source into parallel
light is provided.
[0028] With this configuration, it is possible to convert the light
emitted from the light source into parallel light and make the
parallel light incident on the diffractive optical element.
[0029] It is preferable that an afocal optical system is arranged
between the light source and the diffractive optical element.
[0030] With this configuration, it is possible to efficiently make
the light emitted from the light source incident on the diffractive
optical element while adjusting the size (the spot diameter) of the
light.
[0031] Another aspect of the invention is directed to a projector
including: a illumination device configured to emit illumination
light; a light modulating device configured to form image light
obtained by modulating the illumination light according to image
information; and a projection optical system configured to project
the image light. The illumination device described in the aspect
explained above is used as the illumination device.
[0032] With the configuration of the projector, it is possible to
perform display excellent in image quality and further reduce the
size of the projector.
[0033] The light emitted from the light source may be linearly
polarized light. A liquid crystal panel may be used as the light
modulating device.
[0034] With the configuration, it is possible to make the
illumination light emitted from the illumination device incident on
the liquid crystal panel without using a polarization conversion
element or the like. Therefore, it is possible to further reduce
the size of the projector while reducing the number of
components.
[0035] A plurality of the illumination devices and a plurality of
the light modulating devices may be arranged for respective
illumination lights having different wavelength regions. The
projector may further include a combining optical system configured
to combine image lights modulated for the respective illumination
lights having the different wavelength regions.
[0036] With this configuration, it is possible to display a color
video (image) using the image lights modulated for the respective
illumination lights having the different wavelength regions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0038] FIG. 1 is a plan view showing the schematic configuration of
a projector.
[0039] FIG. 2 is a plan view showing the schematic configuration of
a illumination device.
[0040] FIGS. 3A to 3C are optical path diagrams for explaining the
arrangement of a diffractive optical element, a superimposing
optical system, and a light modulating device.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0041] An embodiment of the invention is explained in detail below
with reference to the drawings.
[0042] Note that, in the drawings used in the following
explanation, characteristic portions are sometimes enlarged and
shown for convenience to clearly show characteristics. Dimension
ratios and the like of components are not always the same as actual
ones.
Projector
[0043] First, an example of a projector 100 shown in FIG. 1 is
explained.
[0044] FIG. 1 is a plan view showing the schematic configuration of
the projector 100.
[0045] The projector 100 is a projection type image display
apparatus that displays a color video (image) on a screen (a
projection surface) SCR. As a light source of a illumination device
included in the projector 100, a laser light source such as a
semiconductor laser (LD), with which high-luminance and high-power
light can be obtained, is used.
[0046] Specifically, the projector 100 generally includes
illumination devices 101R, 1016, and 101B configured to
respectively emit laser lights (illumination lights) corresponding
to colors of red (R), green (G), and blue (B), light modulating
devices 102R, 102G, and 102B configured to respectively modulate,
according to an image signal, the laser lights emitted from the
illumination devices 101R, 101G, and 101B and form image lights
corresponding to the colors, a combining optical system 103
configured to combine the image lights emitted from the light
modulating devices 102R, 102G, and 102B, and a projection optical
system 104 configured to project image light emitted from the
combining optical system 103 toward the screen SCR.
[0047] The illumination devices 101R, 101G, and 101B basically have
the same configuration except that semiconductor lasers
corresponding to the colors of red (R), green (G), and blue (B) are
used as light sources. The illumination devices 101R, 101G, and
101B emit illumination lights modulated to have a uniform
illuminance distribution toward the light modulating devices 102R,
102G, and 102B.
[0048] The light modulating devices 102R, 102G, and 102B are
configured by liquid crystal light valves (liquid crystal panels).
The light modulating devices 102R, 102G, and 102B respectively form
image lights obtained by modulating illumination lights
corresponding to the colors according to image information. Note
that sheet polarizers (not shown in the figure) are arranged on
incident sides and emission sides of the light modulating devices
102R, 102G, and 102B to allow only linearly polarized lights in
specific directions to pass.
[0049] The combining optical system 103 is configured by a cross
dichroic prism. The image lights emitted from the light modulating
devices 102R, 102G, and 102B are incident on the combining optical
system 103. The combining optical system 103 combines the image
lights corresponding to the colors and emits the combined image
light toward the projection optical system 104.
[0050] The projection optical system 104 is configured by a
projection lens group. The projection optical system 104 magnifies
the image light combined by the combining optical system 103 and
projects the magnified image light toward the screen SCR.
Consequently, a magnified color video (image) is displayed on the
screen SCR.
Illumination Device
[0051] The specific configuration of the illumination devices 101R,
101G, and 101B is explained.
[0052] Note that, as explained above, the illumination devices
101R, 101G, and 101B basically have the same configuration except
that semiconductor lasers corresponding to the colors of red (R),
green (G), and blue (B) are used as light sources. Therefore, in
the following explanation, the illumination device 101R is
explained. Note that FIG. 2 is a plan view showing the schematic
configuration of the illumination device 101R.
[0053] The illumination device 101R generally includes, as shown in
FIG. 2, an array light source 2 in which a plurality of
semiconductor lasers 2a are arrayed, a collimator optical system 3
on which lights L1 emitted from the semiconductor lasers 2a are
incident, an afocal optical system 4 on which the lights L1
converted in to parallel lights by the collimator optical system 3
are incident, a diffractive optical element 5 on which the lights
L1, the size (the spot diameter) of which is adjusted by the afocal
optical system 4, are incident, and a superimposing optical system
6 on which lights (diffracted lights) L2 diffracted by the
diffractive optical element 5 are incident. Lights L3 superimposed
by the superimposing optical system 6 enter the light modulating
device 102R as illumination light.
[0054] The array light source 2 is configured by arranging the
plurality of semiconductor lasers 2a in an array shape in a surface
orthogonal to an optical axis ax1. The laser lights L1 emitted from
the semiconductor lasers 2a are linearly polarized coherent lights.
The laser lights L1 are emitted in parallel to one another.
[0055] The collimator optical system 3 is configured by a plurality
of collimator lenses 3a arranged in an array shape to correspond to
the semiconductor lasers 2a. The laser lights L1 converted into
parallel lights by the collimator lenses 3a are incident on the
afocal optical system 4.
[0056] The afocal optical system 4 is configured by lenses 4a and
4b. The lights L1, the size (the spot diameter) of which is
adjusted by the afocal optical system 4, are incident on the
diffractive optical element 5.
[0057] The diffractive optical element 5 is configured by a
computer generated hologram (CGH). The diffractive optical element
5 is designed such that diffraction efficiency of first order
diffracted light is maximized.
[0058] Note that, as the first order diffracted light, there are
+first order diffracted light and -first order diffracted light.
The diffractive optical element 5 is designed such that diffraction
efficiency of one of the first order diffracted lights is
maximized. When the CGH is used, it is possible to set the
diffraction efficiency of the first order diffracted light to 90%
or higher (ideally, 1000).
[0059] A plurality of the laser lights L1 emitted from the
semiconductor lasers 2a of the array light source 2 are incident on
the diffractive optical element 5. Therefore, a plurality of first
order diffracted lights is emitted from the diffractive optical
element 5. The number of the first order diffracted lights
corresponds to the number of the plurality of laser lights L1.
Principal rays of the first order diffracted lights are parallel to
one another. Therefore, in the invention, unless specifically noted
otherwise, a bundle of the plurality of first order diffracted
lights is treated as one diffracted light L2. A direction of the
principal ray in the center of the diffracted lights L2 is a
direction passing the center of the bundle of the plurality of
first order diffracted lights and parallel to the principal rays of
the first order diffracted lights.
[0060] The diffractive optical element 5 generates a diffracted
light distribution in which a luminous intensity distribution is
formed in a rectangular shape as a whole and an aspect ratio of the
luminous intensity distribution coincides with an aspect ratio of
an illumination target (an image forming region of the light
modulating device). Consequently, it is possible to efficiently
make illumination light formed in a rectangular shape as a whole
incident on image forming regions of the light modulating devices
102R, 102G, and 102B formed in a rectangular shape.
[0061] In the diffractive optical element 5, it is preferable that
the lights L1 are perpendicularly incident on an incident surface
5a of the diffractive optical element 5. The optical axis ax1 is
orthogonal to the light incident surface 5a. Consequently, it is
easy to perform diffractive optical design of the CGH for obtaining
the diffracted lights L2. On the other hand, the direction of the
principal ray in the center of the diffracted lights L2 is tilted
with respect to the optical axis ax1 of the light L1 emitted from
the array light source 2.
[0062] The superimposing optical system 6 is configured by two
lenses, i.e., a superimposing lens 6a and a field lens 6b. The
superimposing optical system 6 is arranged in a state in which an
optical axis ax2 of the superimposing optical system 6 is set to
coincide with the direction of the principal ray in the center of
the diffracted lights L2.
[0063] It is preferable that the direction of the principal ray in
the center of the diffracted lights L2 is tilted at an angle
.theta. of 5 to 20.degree. with respect to the optical axis ax1 of
the lights L1 emitted from the array light source 2. Note that, in
FIG. 2, the angle .theta. is represented as an angle on an acute
angle side formed by the optical axis ax2 and the optical axis ax1.
Consequently, the first order diffracted light having maximum
diffraction efficiency among the diffracted lights L2 emitted from
the diffractive optical element 5 efficiently enters the
superimposing optical system 6.
[0064] The superimposing optical system 6 superimposes the
diffracted lights L2 emitted from the diffractive optical element 5
on the illumination target, and the light modulating device 102R is
irradiated with the superimposed lights L3 that serves as
illumination light.
[0065] In a illumination device 1, the direction of the principal
ray in the center of the diffracted lights L2 coincides with the
optical axis ax2 of the superimposing optical system 6. Therefore,
it is possible to emit illumination light having a more uniform
illuminance distribution while reducing an aberration due to the
superimposing optical system 6.
[0066] The arrangement of the diffractive optical element 5, the
superimposing optical system 6, and the light modulating device
102R is explained with reference to FIGS. 3A to 3C. Note that FIG.
3A is an optical path diagram of first order diffracted lights
emitted from an optical center of the diffractive optical element 5
and the periphery of the optical center S. FIG. 3B is an optical
path diagram of parallel lights coming from the light modulating
device 102R side. FIG. 3C is an optical path diagram of parallel
lights coming from the diffractive optical element 5 side.
[0067] In the illumination device 1, as shown in FIG. 3B, the
diffractive optical element 5 is arranged at a combined front focal
position of a lens group including the lenses 6a and 6b. On the
other hand, as shown in FIG. 3C, the image forming region of the
light modulating device 102R serving as the illumination target is
arranged at a combined rear focal position of the lens group
including the lenses 6a and 6b. Consequently, as shown in FIG. 3A,
it is possible to efficiently make the lights L3 superimposed by
the superimposing optical system 6 incident on the image forming
region of the light modulating device 102R.
[0068] The diffracted light L2 emitted from the diffractive optical
element 5 is formed by a bundle of a plurality of first order
diffracted lights. The first order diffracted lights form
illumination light having a small aberration in the image forming
region of the light modulating device 102R while being superimposed
with one another by the superimposing optical system 6.
Consequently, it is possible to emit illumination light having a
more uniform illuminance distribution toward the image forming
region of the light modulating device 102R.
[0069] In the illumination device 1 having the configuration
explained above, by using the CGH as the diffractive optical
element 5, it is possible to generate illumination lights having a
more uniform illuminance distribution (brightness) while reducing
an aberration due to the superimposing optical system 6. It is
possible to efficiently emit such illumination lights toward the
image forming region of the light modulating device 102R serving as
the illumination target.
[0070] Therefore, it is possible to perform display excellent in
image quality by applying the illumination devices 101R, 101G, and
101B to the projector 100.
[0071] In the projector 100, the lights L1 which are linearly
polarized are emitted from the array light source 2. Therefore, it
is possible to make the illumination lights emitted from the
respective illumination devices 101R, 101G, and 101B respectively
incident on the light modulating devices 102R, 102G, and 102B
without using polarization conversion elements or the like.
Consequently, it is possible to further reduce the size of the
projector 100 while reducing the number of components.
[0072] In the projector 100, it is preferable that the array light
source 2 and the diffractive optical element 5 are arranged such
that, when the direction of the principal ray in the center of the
diffracted lights L2 is set to coincide with the horizontal
direction, the lights L1 emitted from the array light source 2 is
incident on the diffractive optical element 5 from upward to
downward.
[0073] The projector 100 projects, with tilted illumination, an
image relatively bright on the downward side and relatively dark on
the upward side is displayed on the screen SCR. On the other hand,
the illumination devices 101R, 101G, and 101B irradiate the image
forming regions of the light modulating devices 102R, 102G, and
102B with illumination lights relatively bright on the downward
side and relatively dark on the upward side on.
[0074] In this case, the illumination lights is converted into
image lights by passing through the light modulating devices 102R,
102G, and 102B. Further, the image lights are reversed vertically
by the projection optical system 104. Consequently, the image
lights become relatively bright on the upward side and relatively
dark on the downward side on the screen SCR. Therefore, it is
possible to cancel a vertical illuminance distribution which is
caused by the tilted illumination. Therefore, the projector 100 can
perform display more excellent in image quality.
[0075] Note that the invention is not always limited to the
embodiments. Various changes can be made without departing from the
spirit of the invention.
[0076] For example, in the embodiment, the array light source 2 in
which the plurality of semiconductor lasers 2a are arrayed is
explained as an example. However, the light sources included in the
illumination device 1 are not limited to such a configuration and
only have to be light sources that emit lights of linearly
polarized coherent lights. The illumination device 1 may include
only one light source.
[0077] In the embodiment, the projector 100 including the three
light modulating devices 102R, 102G, and 102B is explained as an
example. However, the invention can also be applied to a projector
that displays a color video (image) with one light modulating
device. Further, the light modulating device is not limited to the
liquid crystal panel explained above. For example, a digital mirror
device can also be used.
[0078] The entire disclosure of Japanese Patent Application No.
2013-053728, filed on May 15, 2013 is expressly incorporated by
reference herein.
* * * * *